Method and system for drying a substrate

ABSTRACT

A method and system is described for drying a thin film on a substrate following liquid immersion lithography. Drying the thin film to remove immersion fluid from the thin film is performed prior to baking the thin film, thereby reducing the likely hood for interaction of immersion fluid with the baking process. This interaction has been shown to cause non-uniformity in critical dimension for the pattern formed in the thin film following the developing process.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of and claims the benefit of priorityunder 35 U.S.C. § 120 from U.S. Ser. No. 10/650,729, filed Aug. 29,2003, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and system for drying asubstrate, and, more particularly, to a method and system for drying asubstrate following exposure during immersion lithography.

2. Description of Related Art

In material processing methodologies, pattern etching comprises theapplication of a patterned mask of radiation-sensitive material, such asphotoresist, to a thin film on an upper surface of a substrate, andtransferring the mask pattern to the underlying thin film by etching.The patterning of the radiation-sensitive material generally involvescoating an upper surface of the substrate with a thin film ofradiation-sensitive material and then exposing the thin film ofradiation-sensitive material to a radiation source through a reticle(and associated optics) using, for example, a photolithography system.Then a developing process is performed, during which the removal of theirradiated regions of the radiation-sensitive material occurs (as in thecase of positive photoresist), or the removal of non-irradiated regionsoccurs (as in the case of negative resist) using a base developingsolution, or solvent. The remaining radiation-sensitive material exposesthe underlying substrate surface in a pattern that is ready to be etchedinto the surface. Photolithographic systems for performing theabove-described material processing methodologies have become a mainstayof semiconductor device patterning for the last three decades, and areexpected to continue in that role down to 65 nm resolution, and less.

The resolution (r_(o)) of a photolithographic system determines theminimum size of devices that can be made using the system. Having agiven lithographic constant k₁, the resolution is given by the equationr_(o)=k₁λ/NA,  (1)where λ is the operational wavelength, and NA is the numerical aperturegiven by the equationNA=n·sinθ_(o).  (2)

Angle θ_(o) is the angular semi-aperture of the system, and n is theindex of refraction of the material filling the space between the systemand the substrate to be patterned.

Following equation (1), conventional methods of resolution improvementhave lead to three trends in photolithographic technology: (1) reductionin wavelength λ from mercury g-line (436 nm) to the 193 nm excimerlaser, and further to 157 nm and the still developingextreme-ultraviolet (EUV) wavelengths; (2) implementation of resolutionenhancement techniques (RETs) such as phase-shifting masks, and off-axisillumination that have lead to a reduction in the lithographic constantk₁ from approximately a value of 0.6 to values approaching 0.4; and (3)increases in the numerical aperture (NA) via improvements in opticaldesigns, manufacturing techniques, and metrology. These latterimprovements have created increases in NA from approximately 0.35 tovalues greater than 0.75, with 0.85 expected in the next few years.However, as can be seen in equation (2), for conventional free-spaceoptical systems (i.e., n=1), there is a theoretical limit bounding NA tovalues of one or less.

Immersion lithography provides another possibility for increasing the NAof an optical system, such as a lithographic system. In immersionlithography, a substrate is immersed in a high-index of refraction fluid(also referred to as an immersion medium), such that the space between afinal optical element and the substrate is filled with a high-indexfluid (i.e., n>1). Accordingly, immersion provides the possibility ofincreasing resolution by increasing the NA beyond the free-spacetheoretical limit of one (see equations (1), and (2)).

Due to the inherently lower cost, relatively easy implementation tocurrent exposure tools, and high potential to reach very high resolutionwith reasonable process latitude, liquid immersion lithography hasemerged as a very promising candidate for semiconductor patterningtechnology down to 65 nm, 45 nm, and beyond. However, immersionlithography technology still faces numerous challenges includingselection of an immersion fluid that is compatible with current andfuture photoresists yet free of optical defects (such as micro-bubbles)and sufficiently transparent, and selection of an immersion process thatfacilitates integration with existing exposure systems and tracksystems. Moreover, problems associated with introducing a liquid to thephotolithography process must be identified, and new system componentsand methods for solving or reducing such problems must be developed.

SUMMARY OF THE INVENTION

One object of the present invention is to address any or all of theabove-described challenges of immersion lithography technology.

Another object of the present invention is to identify problemsassociated with introducing a liquid to the photolithographic process,and to provide system components and/or process steps for solving orreducing such problems.

Yet another object of the present invention is to improve the uniformityof a pattern formed in a thin film by immersion lithography.

A method and system for drying a substrate following immersionlithography is described.

These and other objects of the present invention are provided by amethod and system for treating an exposed thin film on a substratefollowing liquid immersion lithography. The method includes drying thesubstrate to remove immersion liquid from the exposed thin film on thesubstrate.

In another aspect, a method of transferring a pattern to a thin film ofradiation-sensitive material on a substrate using photolithographyincludes exposing the thin film to a radiation source in a liquidimmersion lithography system, and drying the substrate following theexposure in the liquid immersion lithography system.

In another aspect, a method of patterning a substrate includes forming athin film of radiation-sensitive material on the substrate; exposing thethin film to a pattern in a liquid immersion lithography system; dryingthe substrate following the exposure in the liquid immersion lithographysystem; baking the substrate following the drying; and developing thethin film on the substrate to form the pattern in the thin film bysubjecting the substrate to a developing solution.

In another aspect, a system for patterning a radiation-sensitivematerial on a substrate for semiconductor manufacturing includes aliquid immersion lithography system configured to expose the thin filmto a pattern; a track system coupled to the liquid immersion lithographysystem and configured for coating the substrate with the thin film priorto the exposure, and developing the pattern in the thin film followingthe exposure; and a drying system coupled to at least one of the liquidimmersion lithography system and the track system, wherein the dryingsystem is configured to substantially remove immersion fluid from thethin film.

In another aspect, a system for irradiating a pattern on a thin film ofradiation-sensitive material on a substrate includes a liquid immersionlithography system configured to expose the thin film on the substrateto the pattern; and a drying system coupled to the liquid immersionlithography system, and configured to dry the thin film following theexposure.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 presents a schematic view of a patterning system according to anembodiment of the present invention;

FIG. 2 presents a schematic view of a patterning system according toanother embodiment of the present invention;

FIG. 3 presents a schematic view of a patterning system according toanother embodiment of the present invention;

FIG. 4 shows a drying system according to another embodiment of thepresent invention;

FIG. 5 presents a method of patterning a substrate according to anotherembodiment of the present invention; and

FIG. 6 presents a computer system upon which an embodiment of thepresent invention can be implemented.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Embodiments of the present invention will be described in detail belowwith reference to the accompanying drawings. As an embodiment accordingto the present application, a patterning system for forming a pattern ina thin film on a substrate, such as a semiconductor substrate forelectronic device manufacturing, is described below.

In conventional lithography processes used for patterning a thin film ofradiation-sensitive material, such as chemically amplified photoresist,a substrate is coated with the thin film of radiation-sensitivematerial, and it is cured in a post-application bake (PAB). The curedthin film is then exposed to a pattern in the lithography system,followed by a cure in a post-exposure bake (PEB) to, for example,promote acid diffusion to control resolution and eliminate standingwaves formed in the vertical profile of the pattern sidewalls.Thereafter, the exposed thin film is developed in a developing solution,and rinsed to remove any defects. In current integrated circuit (IC)manufacturing projections using this conventional lithography process,patterning technology at 0.15 micron is expected to achieveapproximately 20 million transistors per square centimeter. Assuming asquare piece of real estate on a silicon substrate for preparing atransistor, the above projections translate into a lateral dimension ofapproximately 2200 nm.

With the advent of advanced lithography technology (such as liquidimmersion technology) for critical dimensions less than 65 nm, scalingthe above results for conventional photolithography enables achieving alateral dimension for a transistor less than 1000 nm. In evaluatingliquid immersion lithography processes, however, the present inventorsdetermined that performing liquid immersion lithography using theconventional PEB step described above leads to non-uniformcharacteristics of the patterned thin film. In particular, the presentinventors discovered that, when using liquid immersion lithographysystems, the exposed thin film on the substrate retains some immersionfluid on a surface thereof, which, in general, is non-uniformlydistributed upon the surface due to the unstable movement of a fluid ona flat surface. Once the substrate exits the exposure system and passesto the PEB system, the subsequent interaction between the non-uniformlydistributed immersion fluid with the bake process leads to a non-uniformdistribution of the pattern formed in the thin film.

More specifically, the present inventors discovered that thenon-uniformly distributed immersion fluid can affect a non-uniformtemperature distribution during the baking process and, ultimately, leadto a non-uniform distribution of the critical dimension (CD) for thepattern formed in the thin film. For example, in regions where excessimmersion fluid is retained, a decrease in the film temperature,relative to other regions in the thin film, is expected during the PEBprocess. This leads to localized regions of the film where the promotionof acid diffusion is different than other regions, thereby diminishingresolution control and allowing vertical profile standing waves inlocalized regions of the thin film. This further leads to non-uniformcharacteristics of actual devices formed on the substrate.

According to an embodiment of the present invention, FIG. 1 presents apatterning system for patterning a substrate using liquid immersionlithography that reduces or eliminates any or all of the aboveidentified problems by drying the substrate following exposure in theliquid immersion lithography system. As shown in FIG. 1, a patterningsystem 1 includes a track system 10, a liquid immersion lithographysystem 20 coupled to the track system 10, and a drying system 30 coupledto at least one of the track system 10 and the liquid immersionlithography system 20. Additionally, a controller 40 can be coupled tothe track system 10, the liquid immersion lithography system 20, and thedrying system 30, and can, for example, be configured to control eachidentified system according to a process recipe.

Alternatively, as shown in FIG. 2, a patterning system 100 comprises atrack system 110, a liquid immersion lithography system 120 coupled tothe track system 110, and a drying system 130 coupled to at least one ofthe track system 110 and the liquid immersion lithography system 120,wherein the drying system 130 resides as part of the track system 110.Additionally, a controller 140 can be coupled to the track system 110,the liquid immersion lithography system 120, and the drying system 130,and can, for example, be configured to control each identified systemaccording to a process recipe.

Still alternatively, as shown in FIG. 3, a patterning system 200includes a track system 210, a liquid immersion lithography system 220coupled to the track system 210, and a drying system 230 coupled to atleast one of the track system 210 and the liquid immersion lithographysystem 220, wherein the drying system 230 resides as part of the liquidimmersion lithography system 220. Additionally, a controller 240 can becoupled to the track system 210, the liquid immersion lithography system220, and the drying system 230, and can, for example, be configured tocontrol each identified system according to a process recipe.

The track system 10 (110, 210) can include a plurality of units utilizedfor forming the pattern in the thin film of radiation-sensitivematerial. The track system 10 (110, 210) can be configured forprocessing substrate sizes of 100 mm, 200 mm, 300 mm, and greater.Moreover, the track system 10 can be configured for processing 248 nmresists, 193 nm resists, 157 nm resists, EUV resists, (top/bottom)anti-reflective coatings (TARC/BARC), and top coats. The plurality ofunits in the track system 10 (110, 210) can include at least one of afilm coating unit, a post application bake (PAB) unit, a post-exposurebake (PEB) unit, an adhesion coating unit, a cooling unit, a cleaningunit, a rinsing unit, a developing unit, and a transfer system fortransporting substrates to and from units and substrate cassettes. Forexample, the track system 10 can comprise a Clean Track ACT 8, or ACT 12resist coating and developing system commercially available from TokyoElectron Limited (TEL). Other systems and methods for forming aphotoresist film on a substrate are well known to those skilled in theart of spin-on resist technology.

Referring still to FIGS. 1-3, the liquid immersion lithography system 20(120, 220) can include at least one of a radiation source, an imagingsystem, a scanning system, a projection lens system, and a substrateholder. For example, the liquid immersion lithography system can beconfigured in a manner similar to the system described in U.S. PatentApplication No. US 2002/0163629 A1 entitled “Methods and apparatusemploying an index matching medium” by Switkes et al. Additionally, forexample, the liquid immersion lithography system can be configured in amanner similar to the system described in U.S. Pat. No. 5,986,742entitled “Lithographic scanning exposure projection apparatus” byStraaijer et al. (assigned to ASML Lithography B.V.), wherein thelithography system is further configured to retain an immersion fluid inthe space residing between the projection lens system and the substrateas described in greater detail for the interference lithographic systemsgiven in Hoffnagle, “Liquid immersion deep-ultraviolet interferometriclithography”, Journal of Vacuum Science & Technology B 17(6), 3303-3309(1999); Switkes & Rothschild, “Immersion lithography at 157 nm”, Journalof Vacuum Science & technology B 19(6), 2353-2356 (2001); and Owen etal., “⅛ mm optical lithography”, Journal of Vacuum Science & technologyB 10(6), 3032-3036 (1992). Additionally, for example, the liquidimmersion lithography system 20 can be derived from any suitableconventional stepping lithographic system, or scanning lithographicsystem.

Although the foregoing description is given with reference to an imagingsystem for pattern transfer in semiconductor manufacturing, it should beunderstood that the liquid immersion lithography system 20 couldalternatively comprise an interferometric lithography system asdescribed in Hoffnagle et al. (1999), and Switkes et al. (2001). Theentire contents of each of the above-described references is herebyincorporated herein by reference.

Referring now to FIG. 4, the drying system 30 (130, 230) includes adrying unit 400 having a drying chamber 410, and a substrate holder 420coupled to the drying chamber 410 and configured to support a substrate430. Substrate holder 420 is further configured to rotate (or spin)substrate 430 during the drying process. A drive assembly 422 coupled tothe substrate holder 420 is configured to rotate the substrate holder420. The drive assembly 422 can, for example, permit setting therotation rate, and the rate of acceleration of the substrate holderrotation. Additionally, drying unit 400 can further include a fluiddispensing system 440 for dispensing a drying fluid, such as alcohol(e.g., isopropyl alcohol), onto the substrate surface to aid indisplacing the immersion fluid thereon. Furthermore, the drying unit 400can include a control system 450 coupled to the drying unit 410, thedrive assembly 422, and the fluid dispensing system 440, wherein it canbe configured to execute one or more process steps for the dryingprocess according to a process recipe.

Referring again to FIGS. 1 through 3, controller 40 (140, 240) includesa microprocessor, memory, and a digital I/O port (potentially includingD/A and/or A/D converters) capable of generating control voltagessufficient to communicate and activate inputs to the track system 10(110, 210) and the liquid immersion lithography system 20 (120, 220) aswell as monitor outputs from these systems. A program stored in thememory is utilized to interact with the systems 10 and 20 according to astored process recipe. One example of controller 40 is a DELL PRECISIONWORKSTATION 530™, available from Dell Corporation, Austin, Tex. Thecontroller 40 may also be implemented as a general purpose computer suchas the computer described with respect to FIG. 6.

Controller 40 may be locally located relative to the track system 10 andthe liquid immersion lithography system 20, or it may be remotelylocated relative to the track system 10 and the liquid immersionlithography system 20 via an internet or intranet. Thus, controller 40can exchange data with the track system 10 and the liquid immersionlithography system 20 using at least one of a direct connection, anintranet, and the internet. Controller 40 may be coupled to an intranetat a customer site (i.e., a device maker, etc.), or coupled to anintranet at a vendor site (i.e., an equipment manufacturer).Furthermore, another computer (i.e., controller, server, etc.) canaccess controller 40 to exchange data via at least one of a directconnection, an intranet, and the internet.

Referring now to FIG. 5, a method of patterning a thin film on asubstrate is described. The method of FIG. 5 may be performed by any oneof the systems described with respect to FIGS. 1-4. The method includesa flow chart 500 beginning in 510 with forming the thin film ofradiation-sensitive material on the substrate. The thin film can beformed using spin coating techniques employed by a track system, such asthe one described in FIGS. 1 through 3. Following the coating process,the thin film can, for example, be cured by baking the film in a PABunit.

In 520, the thin film of radiation-sensitive material is exposed to apattern in a liquid immersion lithography system, such as any of thesystems described above.

In 530, following the radiation exposure, the thin film on the substrateis dried in a drying system, such as the one described in FIG. 4. Thedrying process includes positioning the substrate on a substrate holder,and rotating the substrate. The substrate can be accelerated to a firstrotation rate, and spun for a first period of time until the immersionfluid is removed from the surface of the thin film by centrifugalforces. Alternatively, the substrate can be accelerated to a firstrotation rate, and spun for a first period of time, followed byacceleration or deceleration to a second rotation rate, and spinning fora second period of time. For example, the first rotation rate cancomprise a low speed rotation rate in order to uniformly spread theimmersion fluid across the surface of the thin film, and the secondrotation rate can be a high speed rotation rate in order to spin off theimmersion fluid. Alternatively, a drying fluid can be dispensed upon thesurface of the thin film, either when rotating or not rotating thesubstrate, in order to displace the immersion fluid. The drying fluidcan be in a gaseous state, or a liquid state. The drying fluid can, forexample, comprise an alcohol, such as isopropyl alcohol. However, anydrying fluid having a vapor pressure higher than that of the immersionfluid can be utilized to aid in removing the immersion fluid from thesurface of the thin film. For instance, the immersion fluid can comprisewater for 193 nm processes, and perfluoropolyether (PFPE) for 157 nmprocesses.

In 540, the thin film can be thermally treated in a PEB unit in orderto, for example, promote acid diffusion to control pattern resolution,and eliminate standing waves in the vertical profile of the patternsidewall.

In 550, the thin film can be developed in a base developing solution, orsolvent in order to remove the irradiated regions of theradiation-sensitive material (as in the case of positive photoresist),or non-irradiated regions (as in the case of negative photoresist).Thereafter, the developed pattern in the thin film can be rinsed, orcleaned, in order to remove any resist defects, contamination, etc.

Thus, the present inventors have discovered a system and process fordrying a substrate during liquid immersion lithography as describedabove. One advantage that may be obtained by an embodiment of theinventive method or process is that immersion lithography may be used toprovide high density integrated circuits, while maintaining uniformityof elements across the integrated circuit. Thus, the present inventionmay provide a plurality of transistors formed in a semiconductorintegrated circuit, each of each of the plurality of transistors havinga lateral dimension of less than 1000 nm and including a plurality offeatures having a critical dimension of less than 65 nm. In such anintegrated circuit provided by an embodiment of the invention, thecritical dimension of each of the plurality of features is substantiallyuniform throughout substantially the entire semiconductor-integratedcircuit.

Although, the drying process is described for photoresist technologies,it can further be applied to any (top) anti-reflective coating (TARC),such as Clariant AZ Aquatar ARC offered by MicroChemicals GmbH(Schillerstrasse 18, D-89077 Ulm, Germany), contrast enhancementmaterial, or any topcoat that is utilized to protect a photoresistlayer, or eliminate thin film interference during lithography.

FIG. 6 illustrates a computer system 1201 upon which an embodiment ofthe present invention may be implemented. The computer system 1201, inwhole or in part, may be used as the controller 40 (140, 240, 450) toperform any or all of the functions of the controller described above.The computer system 1201 includes a bus 1202 or other communicationmechanism for communicating information, and a processor 1203 coupledwith the bus 1202 for processing the information. The computer system1201 also includes a main memory 1204, such as a random access memory(RAM) or other dynamic storage device (e.g., dynamic RAM (DRAM), staticRAM (SRAM), and synchronous DRAM (SDRAM)), coupled to the bus 1202 forstoring information and instructions to be executed by processor 1203.In addition, the main memory 1204 may be used for storing temporaryvariables or other intermediate information during the execution ofinstructions by the processor 1203. The computer system 1201 furtherincludes a read only memory (ROM) 1205 or other static storage device(e.g., programmable ROM (PROM), erasable PROM (EPROM), and electricallyerasable PROM (EEPROM)) coupled to the bus 1202 for storing staticinformation and instructions for the processor 1203. The computer systemmay also include one or more digital signal processors (DSPs) such asthe TMS320 series of chips from Texas Instruments, the DSP56000,DSP56100, DSP56300, DSP56600, and DSP96000 series of chips fromMotorola, the DSP1600 and DSP3200 series from Lucent Technologies or theADSP2100 and ADSP21000 series from Analog Devices. Other processorsspecially designed to process analog signals that have been converted tothe digital domain may also be used.

The computer system 1201 also includes a disk controller 1206 coupled tothe bus 1202 to control one or more storage devices for storinginformation and instructions, such as a magnetic hard disk 1207, and aremovable media drive 1208 (e.g., floppy disk drive, read-only compactdisc drive, read/write compact disc drive, compact disc jukebox, tapedrive, and removable magneto-optical drive). The storage devices may beadded to the computer system 1201 using an appropriate device interface(e.g., small computer system interface (SCSI), integrated deviceelectronics (IDE), enhanced-IDE (E-IDE), direct memory access (DMA), orultra-DMA).

The computer system 1201 may also include special purpose logic devices(e.g., application specific integrated circuits (ASICs)) or configurablelogic devices (e.g., simple programmable logic devices (SPLDs), complexprogrammable logic devices (CPLDs), and field programmable gate arrays(FPGAs)).

The computer system 1201 may also include a display controller 1209coupled to the bus 1202 to control a display 1210, such as a cathode raytube (CRT), for displaying information to a computer user. The computersystem includes input devices, such as a keyboard 1211 and a pointingdevice 1212, for interacting with a computer user and providinginformation to the processor 1203. The pointing device 1212, forexample, may be a mouse, a trackball, or a pointing stick forcommunicating direction information and command selections to theprocessor 1203 and for controlling cursor movement on the display 1210.In addition, a printer may provide printed listings of data storedand/or generated by the computer system 1201.

The computer system 1201 performs a portion or all of the processingsteps of the invention in response to the processor 1203 executing oneor more sequences of one or more instructions contained in a memory,such as the main memory 1204. Such instructions may be read into themain memory 1204 from another computer readable medium, such as a harddisk 1207 or a removable media drive 1208. One or more processors in amulti-processing arrangement may also be employed to execute thesequences of instructions contained in main memory 1204. In alternativeembodiments, hard-wired circuitry may be used in place of or incombination with software instructions. Thus, embodiments are notlimited to any specific combination of hardware circuitry and software.

As stated above, the computer system 1201 includes at least one computerreadable medium or memory for holding instructions programmed accordingto the teachings of the invention and for containing data structures,tables, records, or other data described herein. Examples of computerreadable media are compact discs, hard disks, floppy disks, tape,magneto-optical disks, PROMs (EPROM, EEPROM, flash EPROM), DRAM, SRAM,SDRAM, or any other magnetic medium, compact discs (e.g., CD-ROM), orany other optical medium, punch cards, paper tape, or other physicalmedium with patterns of holes, a carrier wave (described below), or anyother medium from which a computer can read.

Stored on any one or on a combination of computer readable media, thepresent invention includes software for controlling the computer system1201, for driving a device or devices for implementing the invention,and for enabling the computer system 1201 to interact with a human user(e.g., print production personnel). Such software may include, but isnot limited to, device drivers, operating systems, development tools,and applications software. Such computer readable media further includesthe computer program product of the present invention for performing allor a portion (if processing is distributed) of the processing performedin implementing the invention.

The computer code devices of the present invention may be anyinterpretable or executable code mechanism, including but not limited toscripts, interpretable programs, dynamic link libraries (DLLs), Javaclasses, and complete executable programs. Moreover, parts of theprocessing of the present invention may be distributed for betterperformance, reliability, and/or cost.

The term “computer readable medium” as used herein refers to any mediumthat participates in providing instructions to the processor 1203 forexecution. A computer readable medium may take many forms, including butnot limited to, non-volatile media, volatile media, and transmissionmedia. Non-volatile media includes, for example, optical, magneticdisks, and magneto-optical disks, such as the hard disk 1207 or theremovable media drive 1208. Volatile media includes dynamic memory, suchas the main memory 1204. Transmission media includes coaxial cables,copper wire and fiber optics, including the wires that make up the bus1202. Transmission media also may also take the form of acoustic orlight waves, such as those generated during radio wave and infrared datacommunications.

Various forms of computer readable media may be involved in carrying outone or more sequences of one or more instructions to processor 1203 forexecution. For example, the instructions may initially be carried on amagnetic disk of a remote computer. The remote computer can load theinstructions for implementing all or a portion of the present inventionremotely into a dynamic memory and send the instructions over atelephone line using a modem. A modem local to the computer system 1201may receive the data on the telephone line and use an infraredtransmitter to convert the data to an infrared signal. An infrareddetector coupled to the bus 1202 can receive the data carried in theinfrared signal and place the data on the bus 1202. The bus 1202 carriesthe data to the main memory 1204, from which the processor 1203retrieves and executes the instructions. The instructions received bythe main memory 1204 may optionally be stored on storage device 1207 or1208 either before or after execution by processor 1203.

The computer system 1201 also includes a communication interface 1213coupled to the bus 1202. The communication interface 1213 provides atwo-way data communication coupling to a network link 1214 that isconnected to, for example, a local area network (LAN) 1215, or toanother communications network 1216 such as the Internet. For example,the communication interface 1213 may be a network interface card toattach to any packet switched LAN. As another example, the communicationinterface 1213 may be an asymmetrical digital subscriber line (ADSL)card, an integrated services digital network (ISDN) card or a modem toprovide a data communication connection to a corresponding type ofcommunications line. Wireless links may also be implemented. In any suchimplementation, the communication interface 1213 sends and receiveselectrical, electromagnetic or optical signals that carry digital datastreams representing various types of information.

The network link 1214 typically provides data communication through oneor more networks to other data devices. For example, the network link1214 may provide a connection to another computer through a localnetwork 1215 (e.g., a LAN) or through equipment operated by a serviceprovider, which provides communication services through a communicationsnetwork 1216. The local network 1214 and the communications network 1216use, for example, electrical, electromagnetic, or optical signals thatcarry digital data streams, and the associated physical layer (e.g., CAT5 cable, coaxial cable, optical fiber, etc). The signals through thevarious networks and the signals on the network link 1214 and throughthe communication interface 1213, which carry the digital data to andfrom the computer system 1201 maybe implemented in baseband signals, orcarrier wave based signals. The baseband signals convey the digital dataas unmodulated electrical pulses that are descriptive of a stream ofdigital data bits, where the term “bits” is to be construed broadly tomean symbol, where each symbol conveys at least one or more informationbits. The digital data may also be used to modulate a carrier wave, suchas with amplitude, phase and/or frequency shift keyed signals that arepropagated over a conductive media, or transmitted as electromagneticwaves through a propagation medium. Thus, the digital data may be sentas unmodulated baseband data through a “wired” communication channeland/or sent within a predetermined frequency band, different thanbaseband, by modulating a carrier wave. The computer system 1201 cantransmit and receive data, including program code, through thenetwork(s) 1215 and 1216, the network link 1214, and the communicationinterface 1213. Moreover, the network link 1214 may provide a connectionthrough a LAN 1215 to a mobile device 1217 such as a personal digitalassistant (PDA) laptop computer, or cellular telephone.

Although only certain exemplary embodiments of this invention have beendescribed in detail above, those skilled in the art will readilyappreciate that many modifications are possible in the exemplaryembodiments without materially departing from the novel teachings andadvantages of this invention. Accordingly, all such modifications areintended to be included within the scope of this invention.

1. A method of transferring a pattern to a thin film ofradiation-sensitive material on a substrate using photolithographycomprising: exposing said thin film to a radiation source in a liquidimmersion lithography system; and dispensing a drying fluid from a fluiddispensing system onto a surface of said substrate following saidexposure in said liquid immersion lithography system to remove animmersion fluid from said substrate, said drying fluid having a vaporpressure higher than a vapor pressure of said immersion fluid.
 2. Themethod of claim 1, further comprising rotating said substrate.
 3. Themethod of claim 2, wherein said rotating comprises rotating saidsubstrate at a first rotation rate for a first period of time, androtating said substrate at a second rotation rate for a second period oftime.
 4. The method of claim 3, wherein said first rotation ratefacilitates distributing said immersion fluid on said thin film, andsaid second rotation rate facilitates removing said immersion fluid fromsaid thin film.
 5. The method of claim 1, wherein said dispensingcomprises dispensing a liquid drying fluid on said substrate.
 6. Themethod of claim 5, wherein said dispensing comprises dispensingisopropyl alcohol on said substrate.
 7. The method of claim 1, whereinsaid dispenses comprises dispensing a gas drying fluid on saidsubstrate.
 8. The method of claim 1, further comprising: baking saidsubstrate following said dispensing in order to promote acid diffusionin said thin film.
 9. The method of claim 1, wherein said exposingcomprises exposing a radiation-sensitive material including at least oneof a 248 nm photoresist, a 193 nm photoresist, a 157 nm photoresist, anextreme ultraviolet (EUV) photoresist, an anti-reflective coating, acontrast enhancement material, a top coat for protecting a photoresist,and a top coat for eliminating thin film interference during exposure.10. A method of treating an exposed thin film on a substrate followingliquid immersion lithography, comprising: dispensing a drying fluid froma fluid dispensing system onto a surface of said substrate to removeimmersion liquid from said exposed thin film on said substrate, saiddrying fluid having a vapor pressure higher than a vapor pressure ofsaid immersion liquid.
 11. The method of claim 10, wherein saiddispensing comprises dispensing a liquid drying fluid on said substrate.12. The method of claim 10, wherein said dispensing comprises dispensinga gas drying fluid on said substrate.
 13. A drying system configured toremove immersion fluid from a substrate following exposure of thesubstrate in a liquid immersion lithography system, the drying systemcomprising: a drying chamber; a substrate holder positioned within thedrying chamber, and configured to hold the substrate; a drying fluiddispensing system configured to dispense a drying fluid onto a surfaceof the substrate, the drying fluid having a vapor pressure higher than avapor pressure of the immersion fluid.
 14. The system of claim 13,further comprising a spin drive configured to rotate said substrateholder.
 15. The system of claim 14, further comprising a controllerconfigured to control the spin drive to rotate said substrate at a firstrotation rate for a first period of time, and rotate said substrate at asecond rotation rate for a second period of time.
 16. The system ofclaim 13, wherein said drying fluid dispensing system is positionedabove said substrate holder.
 17. The system of claim 16, wherein thedrying fluid dispensing system is configured to dispense a liquid. 18.The system of claim 16, wherein the drying fluid dispensing system isconfigured to dispense a gas.
 19. The system of claim 17, wherein saiddrying fluid dispensing system is configured to dispense isopropylalcohol.
 20. A semiconductor integrated circuit comprising: a pluralityof transistors formed in said semiconductor integrated circuit, each ofsaid plurality of transistors having a lateral dimension of less than1000 nm and including a plurality of features having a criticaldimension of less than 65 nm, wherein said semiconductor integratedcircuit is produced from the method claimed in claim 1.